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Analysis of equations of motion by Moczo et al. (2022) led to the conclusion that the discrete (grid) representation of the heterogeneous medium must be wavenumber bandlimited up to the Nyquist frequency. This is a consequence of the spatial discretization. Mittet (2021a) reported that if the discrete grid model of medium coincides with the true medium up to some wavenumber, the simulated wavefield is accurate only up to a half of this wavenumber. Here, we present results of the systematic and comprehensive analysis focused on the principal limits of accuracy of numerically simulated wavefields. First, we analyze wavenumber spectra of (1) exact wavefields in a heterogeneous elastic medium, (2) wavenumber bandlimited wavefields, and (3) spatially discretized wavefields. Then, we derive spatial dependence of the frequency spectrum of waves generated by a finite source, and perturbing wavefields due to a small perturbation of the medium and due to a small wavenumber bandlimited perturbation of the medium. We analyze an interaction of an incoming wave with the medium perturbation through a change of phase difference and through wavenumber spectra. We draw conclusions on the wavenumber limitation of wavefields in the wavenumber bandlimited heterogeneous medium. We numerically verify the fundamental finding using exact solutions. The main consequence for the finite-difference (FD) modeling based on spatial discretization of the computational domain is: Due to spatial sampling, the medium must be wavenumber limited up to the Nyquist frequency. Then, the wavefield should not be sampled by less than four spatial grid spacings per shortest wavelength to obtain sufficiently accurate results. This applies to any heterogeneous FD scheme. [ABSTRACT FROM AUTHOR]

This study was conducted to apply the finite volume method (FVM) to solve the partial differential equation (PDE) governing the heat transfer process during meat cooking with convective surface conditions. For a one‐dimensional, round‐shaped food, such as meat balls, the domain may be divided into shells of equal thickness, with energy balance established for each adjacent shell using in the finite difference scheme (FDS) to construct a set of finite difference equations, which were then solved simultaneously using the FORTRAN language and the IVPAG subroutine of the International Mathematics and Statistics Library. The FDS is flexible for temperature‐dependent physical properties of foods, such as thermal conductivity (k), specific heat (Cp), thermal diffusivity (α), and boundary conditions, for example, surface heat transfer coefficient (h), to predict the dynamic temperature profiles in beef and chicken meat balls cooked in an oven. Once the FVM model was established and validated, it was used to simulate the dynamic temperature profiles during cooking, which were then used in combination with the general method to evaluate the thermal lethality of Shiga toxin‐producing Escherichia coli and Salmonella spp. using D and z values in ground meats during cooking. The method can be applied to design cooking processes that effectively inactivate foodborne pathogens while maintaining the quality of cooked meats and evaluate the adequacy of a cooking process. Practical Application: The temperature dependences of thermal conductivity (k) and thermal diffusivity (α) of raw ground beef and ground chicken meats were measured. These thermal properties were then used in numerical simulation to predict the dynamic heating temperature profile and thermal lethality of ground beef and chicken meat balls. The numerical simulation method may be used to optimize and evaluate thermal processes and ensure the inactivation of pathogens in meat products during cooking. [ABSTRACT FROM AUTHOR]

21,40We have implemented and verified a parallel-series Iwan-type nonlinear model in a 3D fourth-order staggered-grid velocity-stress finite-difference method. The Masing unloading and reloading behavior is simulated by tracking an overlay of concentric von Mises yield surfaces. Lamé parameters and failure stresses pertaining to each surface are calibrated to reproduce the stress-strain backbone curve, which is controlled by the reference strain assigned to a given depth level. The implementation is successfully verified against established codes for 1D and 2D SH-wave benchmarks. The capabilities of the method for large-scale nonlinear earthquake modeling are demonstrated for an 7.8W 7.8 dynamic rupture ShakeOut scenario on the southern San Andreas fault. Although ShakeOut simulations with a single yield surface reduces long-period ground-motion amplitudes by about 25% inside a waveguide in greater Los Angeles, Iwan nonlinearity further reduces the values by a factor of 2. For example, inside the Whittier Narrows corridor spectral accelerations at a period of 3 s are reduced from 1g in the linear case to about 0.8 in the bilinear case and to 0.3-0.4g in the multisurface Iwan nonlinear case, depending on the choice of reference strain. Normalized shear modulus reductions reach values of up to 50% in the waveguide and up to 75% in the San Bernardino basin at the San Andreas fault. We expect the implementation to be a valuable tool for future nonlinear 3D dynamic rupture and ground-motion simulations in models with coupled source, path, and site effects. [ABSTRACT FROM AUTHOR]

High temperatures are generated due to the sliding contacts between the rubbing surfaces of the friction clutch system. In this work, by considering the effective thermal contact conductance under sliding conditions, a simulation model of a two-dimensional transient temperature field of the clutch disc was developed. A numerical solution to obtain the surface temperature at different radii was presented based on the finite difference method. Compared with the experimental data, the proposed model for estimating the surface temperature is more accurate than the conventional prediction method. The results showed that the errors of the calculated temperatures at radii of 114 and 106 mm have obviously reduced by 12.98% and 12.60%, respectively. In addition, the influences of pressure and relative speed on the surface temperature were investigated. The temperature increases with the increase of the relative speed and pressure during the sliding period, and there is an interaction effect between pressure and speed on the surface temperature rise. [ABSTRACT FROM AUTHOR]

This paper reports a typical case history of deep braced excavation for constructing the main bridge cushion cap of the Yangwan River Bridge to explore the excavation performance under embankment surcharge load. Three-dimensional finite difference analysis, simulating the whole construction process of this case history, was performed to capture the effects of the embankment–excavation distance, revel level, and excavation bottom sealing on the responses of the earth retaining structure and the ground. It was found that both the ground surface settlement and the retaining structure deformation are larger on the near-embankment side than the far-embankment side. The responses on the near-embankment side are more sensitive to the embankment–excavation distance and the river level. However, the effects of these parameters diminish greatly when the embankment–excavation distance exceeds 1.5 times the excavation depth. The excavation bottom sealing measures can reduce the retaining structure deformation, and effectively restrain basal heave. This restraint weakens as the excavation bottom sealing thickness exceeds 1 m. [ABSTRACT FROM AUTHOR]

Abstract High temperatures are generated due to the sliding contacts between the rubbing surfaces of the friction clutch system. In this work, by considering the effective thermal contact conductance under sliding conditions, a simulation model of a two-dimensional transient temperature field of the clutch disc was developed. A numerical solution to obtain the surface temperature at different radii was presented based on the finite difference method. Compared with the experimental data, the proposed model for estimating the surface temperature is more accurate than the conventional prediction method. The results showed that the errors of the calculated temperatures at radii of 114 and 106 mm have obviously reduced by 12.98% and 12.60%, respectively. In addition, the influences of pressure and relative speed on the surface temperature were investigated. The temperature increases with the increase of the relative speed and pressure during the sliding period, and there is an interaction effect between pressure and speed on the surface temperature rise.

In this study, an accurate and computationally efficient model for the heating process of thin thermoplastic sheets during thermoforming is developed. This model opens the door to efficient training of model-free control approaches in thermoforming applications, which often require extensive training data that would be significantly costly and time-consuming to generate using physical setups. This model takes into account heat transfer via radiation between heaters and the sheet, heat transfer via conduction through the sheet, and heat transfer via convection between the sheet and the ambient. In this paper, rather than using an analytical relationship for the view factor, an experiment is designed to determine the exact radiation pattern of the heater on the sheet and the fraction of infrared emission absorbed by the sheet. Comparing the output temperature profile on the sheet from the designed model to IR images from a laboratory-scale heating system indicates that the mean square error is reduced by around four times when compared to traditional models with analytical view factors. Moreover, a comparison of the computation time with COMSOL software for a scenario with the same configuration of computation hardware reveals that the designed model is almost ten times faster. [ABSTRACT FROM AUTHOR]

Objective. The aim of the study is to build finite-difference models that can be used to test the bending vibrations of a rod under various fastening conditions, solving the problem in the frequency or time domain. Method. The study is based on the application of the finite difference method and the finite element method. Result. The necessity of application is substantiated and the technique of mathematical modeling is proposed for the design engineering of radio-electronic means operating under conditions of dynamic external influences. The significance of the use of discrete models and the peculiarities of their creation for studying the dynamics of certain constructs of electronic equipment are analyzed. The concept of studying simple models of bar structures for the analysis and verification of the theoretical positions of constructing models of structures is proposed. The features in the development of models for the calculation of natural shapes and frequencies of bending vibrations of rods are shown. Conclusion. Assessment of vibration strength and vibration resistance of non-stationary structures of radio-electronic means is possible by methods and means of mathematical modeling used as test models to test various hypotheses and theoretical positions in the study of the dynamics of complex structures and the design of radio-electronic means.

Under high dynamic load, roadway deformation and failure may occur, posing great challenges. As for now, few studies have been carried out on the impacts of various factors on the deformation of roadway surrounding rocks under high dynamic load, not to mention those on intelligent prediction of the deformation and failure laws. This paper fills these research gaps by studying the deformation and failure characteristics of roadway surrounding rocks and the intelligent prediction method under high dynamic load. The finite difference software Flac3D was used to analyze the influences of roadway buried depth, lithology, and side pressure coefficient on the stability of surrounding rocks and a model was constructed for deformation prediction under high dynamic load. Finally, the influence of various factors on the deformation and their weight was obtained and the deformation can be predicted in line with the BP neural network prediction theory. The results show that the prediction effect is good, with high accuracy. [ABSTRACT FROM AUTHOR]

The drained and undrained response of soft clays reinforced with granular columns has been the subject of numerous geotechnical research efforts to date. Although these studies have been essential for the development of design methodologies, the actual/true response of reinforced clay systems under realistic loading rates is likely governed by partially drained conditions that have yet to be investigated. Partial drainage occurs as a result of inevitable radial flow from the clay to the columns throughout the loading phase. Ignoring the positive effect of partial drainage on the short-term stability of foundations and/or embankments on a clay substratum reinforced with free draining columns may lead to over conservative designs. The objective of this study is to investigate the impact of partial drainage on the response of soft clays reinforced with sand column groups. To address this issue, four partially drained triaxial tests were conducted at different strain rates on normally consolidated soft clays reinforced with dense sand columns in a square configuration. Results included the effect of partial drainage on the total deviatoric stress, excess pore water pressure dissipation, volumetric strain, and stress concentration ratio. The results were bracketed between the fully drained and fully undrained responses/graphs that served as upper and lower bounds, respectively. A plot of the normalized improvement index vs tfailure/t50 showed full mobilization of strength at a time ratio of 15. Numerical modeling using finite difference of the pore water pressure dissipation during shearing was conducted. The consolidation results obtained from the numerical analyses were compared to measurements from the experimental program. The calculated degree of consolidation from the finite difference analysis correlated very well with the measured levels of consolidation during the tests. The results from the test program and the associated analyses presented in this paper contribute to enhancing our current understanding of the response of reinforced clay systems and may be a step on the road towards improving existing design methodologies. [ABSTRACT FROM AUTHOR]

Hard rock excavation affects excavation efficiency. During excavation, the cutoff teeth of the tunnel boring machine are severely worn or even fractured. However, the traditional blasting methods of excavation can lead to various safety problems. A new kind of stone crusher is urgently needed in practical engineering. In this study, the finite difference analysis software was employed to analyze the key drilling fracturing parameters (borehole diameter, borehole spacing, and borehole number) and discuss the effect of the rupture zone formed by multiple boreholes on the damage to the surrounding rock. The research results showed that the hard rock was more easily cracked with an increase in the diameter of the drilling hole. Decreasing the hole pitch strengthened the cracking effects, and increasing the number of drilling holes also increased the number of fracture zones. This study might be of great theoretical and practical significance in developing a new kind of stone crusher and enhancing the excavating efficiency. [ABSTRACT FROM AUTHOR]

We update the eastern and the northern portions of the detailed domain of the U.S. Geological Survey San Francisco Bay region 3D seismic velocity model (SFVM) based on comparisons of recorded and synthetic ground motions from 20 moderate (MW 3.7-4.6) earthquakes. We modify the current SFVM (v.08.3.0) by assigning alternate property-versus-depth relations to the existing 3D geologic model. In some places, changes correspond to reassigning correct relations in which geologic units appear to be mislabeled, and in other places we subdivide geologic units where mapped geologic boundaries are missing from the 3D models so that we can implement a velocity contrast across a boundary. We also make ad hoc adjustments to velocity rules near the surface in some areas to better fit arrival times (specifically, in the Livermore basin). The updates reduce misfits in waveform correlation, travel time, cumulative absolute displacement, and peak ground velocity and are included in v.21.1 of the model. The selected earthquakes are small enough so that we neglect finite-source effects and model them as point sources. This allows us to assume that observed waveform characteristics are the result of path effects, and discrepancies between synthetic and recorded motions arise from misrepresentation of the elastic properties. Our analysis suggests refining the 3D geologic model, and adjusting the rules assigning properties to the geologic units will further improve the accuracy of the SFVM for simulating earthquake ground motions. [ABSTRACT FROM AUTHOR]

There is far-reaching equivalence between the source time functions inferred from dynamic rupture simulations and those corresponding to the kinematic models of slip radiating the generalized omega-n spectrum, in which the power n is allowed to take on noninteger values. First, the same two physical parameters of faulting--the final-fault displacement U and the peak rate of slip vm--govern the slip law in both cases. Second, in both models, the widths of the radiated far-field velocity pulses follow close analytical forms. Third, the full variety of temporal shapes of the dynamic source time functions, spanning the entire parameter space, closely corresponds to the variation in the omega-n shapes with n changing from 1.5 to 3.5, approximately. Smaller n lead to the source time functions that reach the maximum value of slip velocity faster: they cause greater asymmetry of the resulting far-field ground-displacement pulse and shorter duration of the positive velocity pulse. Fourth, in the frequency domain, the ωn spectrum, in which n changes in a narrower range from approximately 2 to 2.5, similarly includes nearly the entire range of possible dynamic Fourier spectra. The narrower range in n found in the frequency domain is explained by the constraints on the spectral slope imposed by the specific triangular shape of the dynamic functions. Fifth, in both dynamic and ωn models, the peak rate of slip vm is the parameter exerting dominant effect on the strength of fault's high-frequency radiation, in the identical quantitative manner. It follows that the omega-n model of slip, in which n is allowed to vary, correctly captures the underlying physics of rupture. [ABSTRACT FROM AUTHOR]

In this study, an accurate and computationally efficient model for the heating process of thin thermoplastic sheets during thermoforming is developed. This model opens the door to efficient training of model-free control approaches in thermoforming applications, which often require extensive training data that would be significantly costly and time-consuming to generate using physical setups. This model takes into account heat transfer via radiation between heaters and the sheet, heat transfer via conduction through the sheet, and heat transfer via convection between the sheet and the ambient. In this paper, rather than using an analytical relationship for the view factor, an experiment is designed to determine the exact radiation pattern of the heater on the sheet and the fraction of infrared emission absorbed by the sheet. Comparing the output temperature profile on the sheet from the designed model to IR images from a laboratory-scale heating system indicates that the mean square error is reduced by around four times when compared to traditional models with analytical view factors. Moreover, a comparison of the computation time with COMSOL software for a scenario with the same configuration of computation hardware reveals that the designed model is almost ten times faster.

The Barcelona Basic Model (BBM) has been implemented in a finite difference-based computer program to simulate the behavior of unsaturated soils subjected to wetting. The BBM implementation was verified using analytical solutions, and the proposed model has been used to simulate the response of a compacted embankment under complete saturation and suction induced conditions. Numerical analyses indicate that considerable amount of total and differential settlements could develop at the top surface of the embankment. BBM is executed into FLAC2D extending a defined module for modified Cam Clay (MCC) and has been set up an analytical solution for suction-dependent stress and strain. Evaluating the effect of anisotropy and nonlinear apparent tensile strength in unsaturated soils, a modification to BBM formulation has been proposed and optimized by developing numerical analyses to reduce the size of elastic region of loading collapse (LC) curve. Then, an experimental study in the literature is investigated by utilizing comparative curves from BBM and modified BBM indicating well agreement with natural circumstances. As a result of the work presented in this research, finite difference codes with BBM and modified BBM has the capability of simulating the real behavior and is operational being applied to problems associated with earthen structures in unsaturated or partially saturated of expansive soils as a three-phases medium. [ABSTRACT FROM AUTHOR]

The thermal behavior of hollow steel structural members due to the temperature increase has not been investigated and discussed in many design codes. This work presents a study of the hollow and solid steel beams' carrying capacity under elevated temperatures. The material properties of such beams decline under the temperature expected to increase the moments on the beams. The finite difference technique is selected first to analyze the problem. The solved problems cover beams under concentrated point load levels with different end conditions such as cantilever, pin roller, and both ends fixed. The beam response (deflection, bending moment, and normal force) is examined. The finite element analysis was conducted using the DIANA FEA software to study the same problem incorporating material and geometric nonlinearities. It was found that both finite difference and finite element analysis solved the problem accurately when the temperature was under 500°C. It was also found that when the temperature was applied to the beam bottom face the deflection was smaller than when the temperature was applied to the side faces only and the whole section. [ABSTRACT FROM AUTHOR]

Geocells are three-dimensional cellular expandable mats used to improve the load-carrying capacity of weak subgrades. The expanded geocell pockets take the shape of a honeycomb connected to their neighbouring pockets. This manuscript deals with the importance of considering the exact shape of the geocell pockets in three-dimensional numerical modelling. The data for the calibration of the numerical models was obtained through laboratory plate load tests. The numerical simulations were carried out using finite difference software, Fast Lagrangian Analysis of Continua in Three Dimensions (FLAC3D). The walls of the geocell were modelled using geogrid elements having only tensile load capacity. The interfaces between the geocell walls and the infill soils were modelled using Mohr-Coulomb yield criterion. Three shapes of geocell pockets, viz. an exact honeycomb shape and simplified shapes (square and diamond), were considered in the numerical simulations. The numerical models with an exact shape of pockets have shown better agreement with experimental data, while the models with approximated shape overestimated the actual load capacity. The paper describes the modelling approach and the reasons for more accurate numerical predictions with the exact shape of geocell pockets compared to simplified pocket shapes. [ABSTRACT FROM AUTHOR]

SiC/SiC ceramic matrix composites (CMCs) are expected to improve the efficiency of aircraft engines. To confirm the reliability of SiC/SiC CMCs, it is necessary to clarify their physical deterioration in a high-temperature and high-humidity environment that simulates an aircraft engine. For the accelerated degradation test of SiC/SiC CMCs, we developed a heating test system, called the Selective Laser Thermoregulation (SLT) system, that uses a fiber laser and a galvano mirror system. This system can adjust the heat input under a steam environment and when the cooling state changes dynamically. We first performed a numerical simulation to design the SLT system and numerically confirmed that it can heat a SiC ceramic sample to over 1400 °C. We then fabricated the proposed system and confirmed that it can heat a SiC ceramic sample to over 1400 °C and safely maintain this temperature. [ABSTRACT FROM AUTHOR]

Urban tunnels crossing faults are always at the risk of severe damages. In this paper, the effects of a reverse and a normal fault movement on a transversely crossing shallow shotcreted tunnel are investigated by 3D finite difference analysis. After verifying the accuracy of the numerical simulation predictions with the centrifuge physical model results, a parametric study is then conducted. That is, the effects of various parameters such as the sprayed concrete thickness, the geo-mechanical properties of soil, the tunnel depth, and the fault plane dip angle are studied on the displacements of the ground surface and the tunnel structure, and on the plastic strains of the soil mass around tunnel. The results of each case of reverse and normal faulting are independently discussed and then compared with each other. It is obtained that deeper tunnels show greater displacements for both types of faulting. [ABSTRACT FROM AUTHOR]

An improved technique of resin delivery, called double-bag progressive compression method (DBPCM), has been developed to manufacture composite parts associated with the vacuum infusion (VI) process. During resin infusion, both bags are pulled upward by the vacuum and the flow resistance offered by the preform is reduced. After the completion of resin infusion, the vacuum on the segmented bags are progressively released to atmospheric pressure allowing the inflated bags to squeeze the surplus resin from the saturated preform. During progressive compression, the dry preform is kept loose and resin easily flows into the preform interstices. Heated air can be utilised at the appropriate compression segment. After the entire preform is wetted, the post-filling stage is carried out to obtain a uniform thickness of the component. This paper describes the numerical results of DBPCM complete filling process in finite difference analysis. The typical VI process is also modelled for comparison purpose. [ABSTRACT FROM AUTHOR]

High intensity rainfall leads to slope failures that are initially unsaturated. Rainfall is the main triggering factor for the slope failure; however, the denseness of the soil with associated soil properties has not received adequate attention on the stability of the slopes. In this study, the finite difference analysis of transient water flow through unsaturated–saturated soil is carried out to study the effects of rainfall intensity and duration on pore pressure generation, degree of saturation, slope stability and shear strain increment during rainfall event. A parametric sensitivity analysis is performed considering three rainfall intensities applied over the soil slopes consisting of three different soil states namely loose, medium and dense. Results indicate that the rainfall affects the stability of loose and medium soil slopes much as compared to the dense soil slope. The rain-induced instability is much more in loose soil slope as compared to the medium soil slope. [ABSTRACT FROM AUTHOR]

This paper presents the three-dimensional finite element modeling of barrette piles in clayey and sandy soils, in which the piles are subjected to statically compressive and uplift loads. Load displacement curves and load transfers were monitored and compared to solutions from one-dimensional finite difference analysis. Capacities of the barrette piles were examined by interpretation methods and bearing capacity equations. Pile load test data of barrette piles located in Xingyi District, Taipei Basin was used for simulation. It was found that the conventional bearing capacity equations are applicable to barrette piles. The interface elements between pile and soils were found to significantly affect the results. Finite element analysis can provide more complete solutions when compared with finite difference analysis. It was also found that the soil frictions due to pile uplift in soft clays at Taipei Basin were underestimated when using common strength reduction ratios. [ABSTRACT FROM AUTHOR]

Abstract In this study, both two-dimensional (2D) and three-dimensional (3D) numerical analyses were carried out to evaluate the performance of geosynthetic-reinforced soil (GRS) piers. The numerical models were first calibrated and verified against test results available in the literature. A parametric study was then conducted under both 2D and 3D conditions to investigate the influences of reinforcement tensile stiffness, reinforcement vertical spacing, and a combination of reinforcement stiffness and spacing on the performance of GRS piers under vertical loading. Numerical results indicated that the effect of reinforcement spacing was more significant than that of reinforcement stiffness. The use of closely – spaced reinforcement layers resulted in higher global elastic modulus of the GRS pier, smaller lateral displacements of pier facing and volumetric change of the GRS pier, lower and more uniformly-distributed tension in the reinforcement, and larger normalized coefficients of lateral earth pressure. This study concluded that a 2D numerical model gave more conservative results than a 3D model. [ABSTRACT FROM AUTHOR]

A mathematical framework has been designed to speculate the physical aspects of a binary chemical reaction (BCR) and Arrhenius activation energy (ACE) on magnetohydrodynamics Williamson micropolar nanofluid flow through a vertical stretching sheet. The fluid viscosity, electrical and thermal conductivity are presumed as reliant temperature function. Furthermore, the Lorentz force is deployed with an angle to the normal of the fluid flow. The natural transformations have been chosen to determine the non-dimensional regular expressions of the model. A conditionally stable finite difference analysis (explicit) is implemented to establish the computational analysis of the transfigured non-linear system of PDEs. The precision of the present numerical solution has been enriched by accomplishing analysis of stability as well as system convergence of finite difference analysis. The graphical representation, along with the tabular depiction, has been done for narrating the physical behaviour of important parameters extensively on various flow fields. The fluctuation of the boundary layer thickness is traced out with the assistance of streamlines, isotherms, and iso-concentration for the impression of the buoyancy ratio parameter and Lewis number. To draw perfection, achieved consequences of the current solution have been contrasted with some subsisting literature. [ABSTRACT FROM AUTHOR]

This paper pertains to the development of a lumped parameter model for predicting the flexural response of a circular footing resting on an engineered reinforced soil bed. The bed is constructed by placing a smooth circular geo-mat over the natural loose sand deposit on which a compacted sand fill is placed. The dense and the loose sand strata are idealized with Winkler springs of different stiffness values. Considering the problem to be axi-symmetric the resulting governing differential equations have been derived and solved for appropriate boundary and continuity conditions by using finite difference technique. Effects of the different parameters like the ratio of flexural rigidity and the dimensions of the footing and the reinforcing element, the ratio of stiffness of the upper and the lower sand layers, and the placement depth of the reinforcement on the settlement and flexural response of the footing have been presented. [ABSTRACT FROM AUTHOR]

This paper introduces the finite difference formulations for the deformations of a surface raft foundation under vertically uniform loads. The thin-plate theory and central difference scheme were adopted to derive the equations in which the finite raft was affected by boundary conditions. With the use of approximate soil springs underneath the raft, none-uniform settlements of the foundation can be analyzed through the newly proposed method. A computer program WERAFT-S is suggested accordingly. Solutions of the analysis were examined with the three-dimensional finite element analysis on numerical models. It was found that the foundation settlements of the newly proposed analysis can be rational by modeling the soils underneath raft as the axial forced elements providing that their stiffness were calibrated carefully prior to the analysis. If the Lysmer's analog model was adopted for the soil springs, much smaller foundation settlements would be resulted at the corners since the analog model is more adequate for rigid footing analysis. Applicability and details of the newly proposed solution are introduced. [ABSTRACT FROM AUTHOR]

Due to inherent spatial variability, soil properties vary from one location to another even within one soil layer. Such spatial variability of soils gives rise to scale-dependency in slope safety evaluation. This paper presents a simplified reliability method for slopes considering spatial soil variability. In this method, equivalent homogeneous random soil parameters are used in a single random variable (SRV) method (e.g., the first-order reliability method) to evaluate the slope reliability. Spatial variability is considered by using the equivalent parameters such that a SRV method with these equivalent parameters produces a comparable failure probability as that calculated using a more rigorous random finite element/difference method (RFEM/RFDM) with the original spatially variable parameters. Empirical equations for determining the statistics (mean value and standard deviation) of the equivalent parameters are derived through extensive RFDM analyses. The proposed method is found to be valid for both single-layered and two-layered slopes. [ABSTRACT FROM AUTHOR]

In this study, the effect of gradual deterioration on the long-term stability of shallow abandoned room and pillar coal mines is investigated. The conventional Tributary Area Method is adopted and modified to take into account the rate of deterioration on the lifetime of pillars. Moreover, a simple quantitative approach is proposed to incorporate the effects of deterioration in numerical modelling. The suggested methods are then used to assess the stability of the shallow abandoned room and pillar coal mines around Dolphingstone village, UK. Results of this study indicate that the gradual deterioration plays a significant role in the long-term stability of shallow abandoned coal mines. The stand-up time of a room and pillar mining panel is also estimated based on the modified Q-system. A good agreement is observed between the results of numerical modelling and the rock mass classification system. [ABSTRACT FROM AUTHOR]

The need for multidisciplinary virtual prototyping in power electronics has been well established, however, design tools capable of facilitating a rapid iterative virtual design process do not exist. A key challenge in developing such tools is identifying and developing modeling techniques which can account for 3-D geometrical design choices without unduly affecting simulation speed. This challenge has been addressed in this paper using model order reduction techniques and a prototype power electronic design tool incorporating these techniques is presented. A relevant electrothermal power module design example is then used to demonstrate the performance of the software and model order reduction techniques. Five design iterations can be evaluated, using 3-D inductive and thermal models, under typical operating and start-up conditions on a desktop PC in less than 15 min. The results are validated experimentally for both thermal and electrical domains. [ABSTRACT FROM PUBLISHER]

This paper presents the development of a 2D finite difference modelling approach and a 3D finite element numerical model for simulating vertical geothermal heat exchangers (GHEs), explaining the theory governing the thermal processes, element discretization and the selection of the appropriate boundary conditions. Both of these models provide fully coupled solutions for the fluid flow in the circulation pipes and the thermal processes between the fluid and solid domains (pipes, grout and soil). The numerical models are verified with a field test and subsequently they are utilized to simulate the thermal performance of a borehole heat exchanger integrated with a single U-tube. Two different thermal operation cases are analyzed; a constant rate heat injection and a fluid injection at a constant temperature. A model validation study is also carried out for the constant rate heat injection case by comparing the numerical results with the available analytical solution for a finite line source. Furthermore, effective thermal conductivity of the ground back-calculated from the results of the numerical analyses is compared with the value used in the numerical models. Comparison of the results obtained from both numerical models and validating model predictions with the analytical solution confirms that both FE and FD models can accurately simulate the heat transfer mechanisms governing the thermal performance of GHE systems. [ABSTRACT FROM AUTHOR]

Although face bolting has been used as a stabilisation technique in open-face tunnelling for decades, there is still a lack of systematic ways for determining the optimum parameters of face bolts. To optimise design for face bolting in soft ground, it is necessary to understand the influences of each parameter associated with face bolting on ground response. In this note, five series of numerical parametric studies are carried out, to investigate the effects of length, density, reinforcement area, axial rigidity of face bolts and strength of soil on tunnel face stability and deformation in soft rock. Based on the ground condition, geometries of tunnel and configurations of face bolts simulated, the optimum length, density and axial rigidity of face bolts are found to be 0.6 H ( H = height of tunnel), 1 bolt/m 2 and 195 MN, respectively. The optimum axial rigidity of face bolt appears to be independent of the bolt density. The computed results also reveal that it is more effective to reduce face deformation by installing face bolts around the tunnel periphery, than installing them near the central area of the tunnel face. [ABSTRACT FROM AUTHOR]

Complex tunnel geometries are very common during the design of urban tunnelling and especially metro lines. Relevant complexities were common during the construction of Athens Metro in Greece, where the need of giving access to trumpet areas, multi-storey underground constructions and transition zones produces special design requirements. Characteristic case histories are the trumpet area as well as the access gallery and chamber to Egaleo Station in the same extension, which are presented in the paper. In both cases, the real challenge was to give solution to underground complex constructions within short lengths of different tunnel profiles. In the first case, a triple-track tunnel splits to a single and a double-track one, while on the second one, a three-storey access gallery was constructed at the north side of Egaleo Station in order to give access for the construction of the station. According to the geology in the area, the Athenian schist was expected, completely weathered on the top and from low to medium strength deeper. The main criteria of the design was to result to a construction methodology such as to assure stability, low surface settlements and convergences, safety, quality and construction advance, within a realistic solution to the constructor. In both cases, the conventional tunnelling method was applied with success, not only regarding the final surface settlements which proved to be small, but also the speed and the convenience in applying on site the designed procedure. [ABSTRACT FROM AUTHOR]

The cone-penetration test (CPT) is a well-established in situ test in geotechnical engineering for soil classification and estimation of soil properties. In a CPT, a cone shaped penetrometer is pushed into the ground at a constant rate. The resistance on the cone tip is measured and is then related to soil classification and soil properties. In this research, the finite difference analysis of large deformations for the cone penetration testing (CPT) in the cohesive soil have been conducted using FLAC 2D Software. In this modeling, interface elements between penetrometer and soil are considered and it is assumed that the penetrometer materials show rigid behavior in reaction to the soil materials. FLAC provides interfaces that are characterized by Coulomb sliding and/or tensile separation. Interfaces have the properties of friction, cohesion, dilation, normal and shear stiffness, and tensile strength there is an in-situ state of stress in the ground, before any excavation or construction is started. In FLAC 2D, an attempt is made to reproduce this in-situ state by setting initial conditions. Ideally, information about the initial state comes from field measurements. Boundary conditions are modeled as axesymmetry. Horizontal and vertical direction at the bottom boundary and horizontal direction at the vertical boundary of soil model are fixed. Soil behavior follows full elastic-plastic model and Mohr-Coulomb failure criterion. Numerical model is analyzed to achieve mesh convergency at the various grids. The values of cone and frictional resistance have been obtained through software calculations and then compared with the results obtained from cone penetration test at the aluminum melt factory in Lamard, Fars Province. Stress and displacement contours are related for evaluation of the penetration process. Steady state is considered to achieve steady stress range in which the hole diameter is equal with the CPT hole. The numerical modeling results of CPT test by FLAC 2D software shows good agreement with the field tests results. Furthermore, the results have been discussed by using Robertson Chart 1986 and Eslami- Felonious Chart 1997. Charts almost show same profile with the field test results at the aluminum melt factory site. [ABSTRACT FROM AUTHOR]

The interpretation method for dilatory dissipation, showing an initial temporary increase in pore pressure, in piezocone tests in overconsolidated clayey soils was investigated in this study. Finite difference analyses on the dissipation after cone penetration were performed with various ground conditions. The spatial distribution of initial excess pore pressure induced by cone penetration was determined from experimental estimations through in-situ tests and laboratory physical model tests and theoretical predictions by the cavity expansion theory and critical state soil mechanics. A method to evaluate the coefficient of consolidation from dilatory dissipation results was developed through the assessment of numerical simulation results. Comparing the application results with the laboratory-determined values, it was verified that the proposed approach provided a reliable and consistent evaluation of the coefficient of consolidation. [ABSTRACT FROM AUTHOR]